Vehicles which utilize electric traction motors to drive wheels of a vehicle, whether the electric motor is in a gas-electric hybrid vehicle or a fuel cell powered vehicle typically use a three-phase AC motor coupled with an inverter that converts direct current from a power source to alternating current. The inverter circuitry generally comprises IGBTs (insulated gate bipolar transistors) mounted on a DBC (direct bonded copper) substrate. The DBC has integrated bus bars, and with a circuit card and signal connector provides a power electronics package.
As automotive vehicles start, change cruising speeds, accelerate and brake, power demands of electric traction motors driving the vehicles fluctuate over a wide range. Fluctuations in power demand cause temperature changes in the inverters connected to the traction motors. Since the inverters comprise IGBTs mounted on the DBCs with integrated bus bars, the inverters are comprised of different materials with various coefficients of expansion. Accordingly, heat fluctuations can degrade inverters as the integrated components thereof expand at different rates tending to shift slightly with respect to one another as the components respond to temperature variations. Accordingly, it is necessary to control temperature to keep expansions and contractions of the components within optimal levels. Currently, this is accomplished by circulating fluids through heat sinks associated with the DBC or by flowing air over the power electronics to absorb and carry away heat. While these approaches currently appear satisfactory, there remains a need to more precisely control the temperature of power electronics over the life of vehicles utilizing traction electric motors in order to sustain reliability of, as well as power consumption by, the vehicles.
There is a continuing effort in configuring automotive vehicles to optimize the use of space within automotive vehicles while facilitating ease of assembly and maintenance. In accomplishing optimal use of space, attempts are made to organize related components into modules, however packaging inverters with motors present a problem because inverters have different cooling requirements.